In the 11 days since the macOS Monterey 12.3 update went live, users have reported issues that the update has bricked Macs with replacement logic boards and encountered issues with game controllers. It now appears that the update is causing issues with external monitors.
Per users on the Apple Support and MacRumors forums, some external displays connected via USB-C are no longer detected by Macs following the macOS Monterey 12.3 update:
After updating my Mac mini today to 12.3, my monitor now no longer displays an image via USB-C, just keeps saying on no signal on the monitor.
I have tried HDMI and same issue. The odd occasion it will display a picture but once I shutdown or restart the mac mini it does not display a picture. The mac is booting up. I have had to resort to connecting it to my old TV with HDMI connection.
This is so frustrating.
Other users have experienced issues with USB-C, HDMI, and DisplayPort connections and have had to switch to lower resolutions for the connection to work:
I’ve solved this problem (on 2022-03-15). On my monitor (LG LCD 27 27UN880-B IPS) I’ve went into settings, and I’ve lowered the DisplayPortVersion from the default v1.4 to v1.2. As soon as I’ve lowered the monitor’s DisplayPortVersion, my Mac with OS X 12.3 has started recognizing the second display correctly. It seems that the new OS X update has issues with a DisplayPortVersion 1.4 protocol (has faster data rate, faster refresh, and stream compression). Hope this helps.
One short-term fix being suggested it to unplug the external display for a short time, plug it back into the Mac, and then plug the display back into a power outlet, after which it should work. Some users have also reported problems when using two external monitors with their Mac.
Apple has yet to publicly comment on the issue.
If you’ve had issues with the macOS 12.3 Monterey update, please let us know about your experiences in the comments.
Via MacRumors and discussions.apple.com